This invention relates generally to refrigeration units, and more specifically to apparatus for supplying a cooling liquid to a condenser of a refrigeration unit.
Normally, the air passing through an air cooled condenser of a refrigeration unit will absorb a sufficient amount of heat from the condenser and the refrigerant flowing therethrough to keep the refrigerant temperature within a desirable range, but occasionally the refrigerant will become overheated. For example, during an excessively hot day such as a day where the outside temperature is above 95.degree. F., the cooling air directed over the condenser is at such an elevated temperature that the required transfer of the heat from the refrigerant to the ambient air does not take place. Even if the ambient temperature is not excessively high, it may well be that dust, film, and the like accumulate to such an extent on the exterior surfaces of the condenser that a layer of insulation is, in effect, formed between the refrigerant passing through the condenser and the the stream of cooling air in which the condenser is located, so that as a result the required heat transfer does not take place.
The result of such insufficient heat transfer is that the normal range of temperature of refrigerant flowing through the refrigeration unit cannot be maintained. Since the pressure of vaporous refrigerant is directly related to the refrigerant temperature, insufficient transfer of heat from the refrigerant to the cooling air also produces undesirably high refrigerant pressures. Operating with such temperatures and pressures, the refrigeration unit, specifically the compressor of the unit, must do more work to satisfy a refrigeration load, increasing the cost of satisfying that load. Further, the refrigeration unit may not be able to completely satisfy the refrigeration load, or the high temperatures and pressures may activate safety switches, rendering the compressor inoperable at a time when the refrigeration unit is most needed.
For this reason, refrigeration units having air cooled condensers are at times equipped with a water spray system wherein a water mist is sprayed over the exterior surfaces of the condenser when the refrigerant flowing through the condenser reaches an objectionably high temperature. Such condensers are generally referred to as evaporative condensers. The water sprayed over the condenser absorbs heat through the condenser surfaces from the refrigerant, helping to maintain the refrigerant temperature at tolerable levels. Typically, the water spray is not continuously needed to maintain the refrigerant temperature at an acceptable level. In order to minimize the amount of water sprayed over the condenser, thereby reducing the operating cost of the spray system, it is desirable to control the water spray so that the spray is employed when needed but left inactive when not needed. Commonly, this is done by sensing one or more of several factors such as the temperature or pressure of the refrigerant flowing through the condenser or the temperature of the ambient air and controlling the water spray in response to the sensed factor.
Prior art condenser spray controls are shown in U.S. Pat. Nos. 2,278,242; 2,551,758; 2,664,715; and 3,613,392. These references, along with U.S. Pat. No. 4,075,865 which is discussed below, appear to be the prior art known to applicant which is most relevant to the present disclosure. The first four of the above-listed patents disclose spray systems in which the control factor is sensed by mechanical elements, including various thermostats, diaphragms, springs, and bellows. As may be appreciated, such mechanical elements are often relatively difficult to manufacture and install, and many times have a comparitively short life span. In addition, mechanical elements may be frequently exposed to and detrimentally affected by factors such as bugs, dust, or dirt, causing the elements to be inaccurate or unreliable.
In accordance with the present invention, an electronic control senses the temperature of refrigerant flowing through an air cooled condenser and controls a water spray associated with the condenser in response to this temperature. Such a water spray control is relatively simple, more reliable, and less expensive than those developed heretofore. The control requires minimal skill in assembly and installation, and includes the inherent advantages such as accuracy and durability which electronic elements have over mechanical devices. By increasing the reliability, accuracy, and durability of the water spary control, the water spray is better able to assist the ambient air, when such assistance is needed, in maintaining the refrigerant within the desired temperature and pressure range and in preventing the development of overload conditions. This, in turn, increases the efficiency and life span of the refrigeration unit as a whole.
The use of an electronic control for a refrigeration unit is disclosed in the last of the above-cited references, U.S. Pat. No. 4,075,865. This patent, however, uses the control to govern the speed of a fan motor of an air cooled condenser to vary the amount of air passed over the condenser. Moreover, the electronic control disclosed in this latter patent is fairly complex, involving an operational amplifier, a light emitting diode, a photo-sensitive transistor, and a plurality of triacs. On the other hand, the electronic control of the present invention is for controlling a water spray system and is comparitively simple. In light of the above discussion and in view of the comments below, it is submitted that the above-listed references do not disclose or suggest the apparatus or method disclosed herein.